Evaluating intra-fractional tumor motion in lung stereotactic radiotherapy with deep inspiration breath-hold.

PURPOSE: To evaluate the intra-fractional tumor motion in lung stereotactic body radiotherapy (SBRT) with deep inspiration breath-hold (DIBH), and to investigate the adequacy of the current planning target volume (PTV) margins. METHODS: Twenty-eight lung SBRT patients with DIBH were selected in this study. Among the lesions, twenty-three were at right or left lower lobe, two at right middle lobe, and three at right or left upper lobe. Post-treatment gated cone-beam computed tomography (CBCT) was acquired to quantify the intra-fractional tumor shift at each treatment. These obtained shifts were then used to calculate the required PTV margin, which was compared with the current applied margin of 5 mm margin in anterior-posterior (AP) and right-left (RL) directions and 8 mm in superior-inferior (SI) direction. The beam delivery time was prolonged with DIBH. The actual beam delivery time with DIBH (Tbeam_DIBH) was compared with the beam delivery time without DIBH (Tbeam_wo_DIBH) for the corresponding SBRT plan. RESULTS: A total of 113 treatments were analyzed. At six treatments (5.3%), the shifts exceeded the tolerance defined by the current PTV margin. The average shifts were 0.0 ± 1.9 mm, 0.1±1.5 mm, and -0.5 ± 3.7 mm in AP, RL, and SI directions, respectively. The required PTV margins were determined to be 4.5, 3.9, and 7.4 mm in AP, RL, and SI directions, respectively. The average Tbeam_wo_DIBH and Tbeam_DIBH were 2.4 ± 0.4 min and 3.6 ± 1.5 min, respectively. The average treatment slot for lung SBRT with DIBH was 25.3 ± 7.9 min. CONCLUSION: Intra-fractional tumor motion is the predominant source of treatment uncertainties in CBCT-guided lung SBRT with DIBH. The required PTV margin should be determined based on data specific to each institute, considering different techniques and populations. Our data indicate that our current applied PTV margin is adequate, and it is possible to reduce further in the RL direction. The time increase of Tbeam_DIBH, relative to the treatment slot, is not clinically significant.

Advances in management of locally advanced cervical cancer.

Globally, cervical cancer has the fourth highest cancer incidence and mortality in women. Cervical cancer is unique because it has effective prevention, screening, and treatment options. This review discusses the current cervical cancer advances with a focus on locally advanced cervical cancer. Topics discussed include diagnostic imaging principles, surgical management with adjuvant therapy and definitive concurrent chemoradiotherapy. Emphasis is given on current advances and future research directions in radiation therapy (RT) with an emphasis on three-dimensional brachytherapy, intensity-modulated RT, image-guided RT, proton RT and hyperthermia.

Active Surveillance for Intermediate Risk Prostate Cancer: Survival Outcomes in the Sunnybrook Experience.

PURPOSE: To assess the applicability of active surveillance in patients with intermediate risk prostate cancer, we compared the survival outcomes of patients with low risk and intermediate risk disease. MATERIALS AND METHODS: Active surveillance was offered to all patients with low risk (cT1-T2b and Gleason score 6 and prostate specific antigen 10 ng/ml or less) and select intermediate risk disease (age greater than 70 years with cT2c or prostate specific antigen 15 ng/ml or less, or Gleason score 3+4 or less). Data from November 1995 to May 2013 were extracted from a prospectively collected database. The primary outcome was metastasis-free survival, and secondary outcomes were overall survival, cause specific survival and treatment-free survival. RESULTS: A total of 213 intermediate risk and 732 low risk cases were identified. Median age was 72 years (IQR 67.3, 76.8) in the intermediate risk cohort and 67 years (IQR 60.6, 71.9) in the low risk group. Median followup was comparable (6.7 years for intermediate risk vs 6.5 years for low risk). Gleason 7 disease comprised 60% of the intermediate risk cohort. The 15-year metastasis-free, overall, cause specific and treatment-free survival rates were inferior in the intermediate risk group (metastasis-free survival HR 3.14, 95% CI 1.51-6.53, p=0.001, 82% for intermediate risk vs 95% for low risk). On further evaluation the estimated 15-year metastasis-free survival for cases of Gleason 6 or less with prostate specific antigen less than 10 ng/ml was 94%, Gleason 6 or less with prostate specific antigen 10 to 20 ng/ml was 94%, Gleason 3+4 with prostate specific antigen 20 ng/ml or less was 84% and Gleason 4+3 with prostate specific antigen 20 ng/ml or less was 63%. CONCLUSIONS: These data support the use of active surveillance in low risk and intermediate risk cases of Gleason 6 but not Gleason 7 prostate cancer. Multiparametric magnetic resonance imaging and novel biomarkers might be vital in detecting favorable Gleason 7 disease.

Assessment of uterus position as a surrogate for high-risk clinical target volume with respect to the applicator position for multiple fractions of brachytherapy in cervical cancer.

AIM: Hybrid magnetic resonance imaging/computerized tomography (MRI/CT) planning for high-dose-rate (HDR) brachytherapy in cervical cancer with MR/CT fusion for the first fraction followed by CT for fraction 2 and 3 is used at our center. The aim of this study is to evaluate the position of applicator intrauterine tube (IU) in relation to uterine serosa with each fraction of intracavitary high-dose-rate brachytherapy. METHODS: Position of the applicator relative to uterus was measured from tip of the applicator (IU) to the top of uterus in the plane of IU and perpendicular to IU in anterior, posterior, left and right directions at the tip of IU, mid-point of the IU and 1 cm from the surface of vaginal ring. The mean absolute difference (±95 % confidence interval) between these positions at fraction 2 and 3 was calculated with fraction one as reference. RESULTS: The mean absolute difference (±95 %) of the applicator relative to uterus was 2.7 ± 0.5 mm at the tip, 1.5 ± 4 mm at mid-point and 1.1 ± 0.3 mm at 1 cm from the surface of the ring. CONCLUSION: This study shows that there is consistency in inter-fraction applicator position relative to uterus apart from at the tip and, therefore, in situations where high-risk clinical target volume (HRCTV) extends towards uterine fundus, MRI should be used for each fraction of brachytherapy planning to accurately define HRCTV.

Tailored Mentorship for the Underrepresented and Allies in Radiation Oncology: The Association of Residents in Radiation Oncology Equity and Inclusion Subcommittee Mentorship Experience.

PURPOSE: There are limited opportunities for mentorship for underrepresented in medicine (URM) trainees and physicians in radiation oncology (RO). The purpose of this study was to create and evaluate a formal mentorship program open to URMs and allies with interests in diversity, equity, and inclusion. METHODS AND MATERIALS: A mentorship program incorporating a virtual platform was designed by the Association of Residents in Radiation Oncology Equity and Inclusion Subcommittee. It was structured to include 6 sessions over 6 months with matched mentor-mentee pairs based on responses to a publicized online interest form. A compilation of evidence-based guidelines was provided to optimize the mentorship relationship. Linked pre- and postprogram surveys were administered to collect demographic data, define baseline goals and level of support, and evaluate program satisfaction. RESULTS: Thirty-five mentor-mentee pairs were matched; 31 mentees completed the preprogram survey and 17 completed the postprogram survey. Preprogram, only 3 mentees (9.7%) reported satisfaction with current mentorship and 5 (16%) reported mechanisms or mentorship in place at their program to support URMs. On the postprogram survey, mentees reported high satisfaction with areas of mentorship, mentor attributes, and the program overall. Opportunities for improvement include implementation of mechanisms to enhance communication with mentor-mentee pairs and maintain longitudinal engagement. CONCLUSIONS: In the first tailored mentorship program in RO for URMs and those with diversity, equity, and inclusion interests, our results demonstrate that there is self-reported interest for better mentorship for URMs in RO, and that a nationwide structured mentorship program can address participants' goals with high satisfaction. Program expansion could provide URMs and allies in RO more opportunities for career development and promote a greater sense of community and inclusion within the field.

Is Substantial Lymphovascular Space Invasion Prognostic in Patients With Pathologically Lymph Node-Negative Endometrial Cancer?

PURPOSE: Lymphovascular space invasion (LVSI) predicts for higher rates of recurrence and increased mortality in endometrial cancer. Using 3-tier LVSI scoring, a PORTEC-1 and -2 trials analysis demonstrated that substantial LVSI was associated with worse locoregional (LR-DFS) and distant metastasis disease-free survival (DM-DFS), and these patients possibly benefited from external beam radiation therapy (EBRT). Furthermore, LVSI is a predictor for lymph node (LN) involvement, but the significance of substantial LVSI is unknown in patients with a pathologically negative LN assessment. We aimed to evaluate clinical outcomes of these patients in relation to the 3-tier LVSI scoring system. METHODS AND MATERIALS: We performed a single-institutional retrospective review of patients with stage I endometrioid-type endometrial cancer who underwent surgical staging with pathologically negative LN evaluation from 2017 to 2019 with 3-tier LVSI scoring (none, focal, or substantial). Clinical outcomes (LR-DFS, DM-DFS, and overall survival) were analyzed using the Kaplan-Meier method. RESULTS: A total of 335 patients with pathologically LN-negative stage I endometrioid-type endometrial carcinoma were identified. Substantial LVSI was present in 17.6% of patients; 39.7% of patients received adjuvant vaginal brachytherapy and 6.9% of patients received EBRT. Adjuvant radiation treatment varied by LVSI status. In patients with focal LVSI, 81.0% received vaginal brachytherapy. Among patients with substantial LVSI, 57.9% received vaginal brachytherapy alone, and 31.6% of patients received EBRT. The 2-year LR-DFS rates were 92.5%, 98.0%, and 91.4% for no LVSI, focal LVSI, and substantial LVSI, respectively. The 2-year DM-DFS rates were 95.5%, 93.3%, and 93.8% for no LVSI, focal LVSI, and substantial LVSI, respectively. CONCLUSIONS: In our institutional study, patients with pathologically LN-negative stage I endometrial cancer with substantial LVSI had similar rates of LR-DFS and DM-DFS compared with patients with none or focal LVSI. These findings highlight the need for multi-institutional studies to validate the prognostic value of substantial LVSI in this patient population.

Indications for Adjuvant Radiation Therapy in Patients With pN0(i +) Adenocarcinoma of the Endometrium.

Sentinel lymph node biopsy has led to an increase in the detection of isolated tumor cells (ITCs) in up to 10% of early stage endometrioid endometrial cancer patients. In addition, the risk of nonsentinel lymph node involvement is approximately 10% or lower in patients with ITCs. In most studies, approximately 60% to 70% of patients with ITCs either underwent completion lymphadenectomy or received adjuvant therapy. Therefore, although multiple studies have shown that the effect of ITCs on disease outcomes is favorable, the true effect of ITCs without additional treatment is not known. In this report we describe our philosophy of relying on extent of surgical nodal staging and presence or absence of adverse intrauterine pathologic factors at the time of adjuvant therapy decision making for endometrioid endometrial carcinoma patients with ITCs.

Radiomic Modeling of Bone Density and Rib Fracture Risk After Stereotactic Body Radiation Therapy for Early-Stage Non-Small Cell Lung Cancer.

Purpose: Our purpose was to determine whether bone density and bone-derived radiomic metrics in combination with dosimetric variables could improve risk stratification of rib fractures after stereotactic body radiation therapy (SBRT) for early-stage non-small cell lung cancer (NSCLC). Methods and Materials: A retrospective analysis was conducted of patients with early-stage NSCLC treated with SBRT. Dosimetric data and rib radiomic data extracted using PyRadiomics were used for the analysis. A subset of patients had bone density scans that were used to create a predicted bone density score for all patients. A 10-fold cross validated approach with 10 resamples was used to find the top univariate logistic models and elastic net regression models that predicted for rib fracture. Results: A total of 192 treatment plans were included in the study with a rib fracture rate of 16.1%. A predicted bone density score was created from a multivariate model with vertebral body Hounsfield units and patient weight, with an R-squared of 0.518 compared with patient dual-energy x-ray absorptiometry T-scores. When analyzing all patients, a low predicted bone density score approached significance for increased risk of rib fracture (P = .07). On competing risk analysis, when stratifying patients based on chest wall V30 Gy and bone density score, those with a V30 Gy ≥30 cc and a low bone density score had a significantly higher risk of rib fracture compared with all other patients (P < .001), with a predicted 2-year risk of rib fracture of 28.6% (95% confidence interval, 17.2%-41.1%) and 4.9% (95% confidence interval, 2.3%-9.0%), respectively. Dosimetric variables were the primary drivers of fracture risk. A multivariate elastic net regression model including all dosimetric variables was the best predictor of rib fracture (area under the curve [AUC], 0.864). Bone density variables (AUC, 0.618) and radiomic variables (AUC, 0.617) have better predictive power than clinical variables that exclude bone density (AUC, 0.538). Conclusion: Radiomic features, including a bone density score that includes vertebral body Hounsfield units and radiomic signatures from the ribs, can be used to stratify risk of rib fracture after SBRT for NSCLC.

Gantry-Based 5-Fraction Elective Nodal Irradiation in Unfavorable-Risk Prostate Cancer: Outcomes From 2 Prospective Studies Comparing SABR Boost With MR Dose-Painted HDR Brachytherapy Boost.

PURPOSE: Guidelines from the American Society of Clinical Oncology and Cancer Care Ontario recommend brachytherapy boost for patients with intermediate-risk or high-risk prostate cancer. SABR is an emerging technique for prostate cancer, but its use in high-risk disease is limited. Efficacy, toxic effects, and quality of life (QoL) were compared in patients treated on 2 prospective protocols that used SABR boost or magnetic resonance-guided high-dose-rate brachytherapy (HDR-BT) boost with 6 to 18 months of androgen deprivation therapy (ADT). METHODS AND MATERIALS: In SATURN study (study 1), patients received 40 Gy to the prostate and 25 Gy to the pelvis in 5 weekly fractions. In SPARE (study 2), patients received HDR-BT (15 Gy × 1) to the prostate and ≤22.5 Gy to the magnetic resonance imaging nodule, followed by 25 Gy in 5 weekly fractions to the pelvis. All patients received between 6 and 18 months of ADT. RESULTS: Thirty patients (7% unfavorable intermediate risk and 93% high risk, per National Comprehensive Cancer Network [NCCN] criteria) completed study 1, and 31 patients (3% favorable intermediate risk, 47% unfavorable intermediate risk, and 50% high risk) completed treatment as per study 2. The median follow-up times were 72 and 62 months, respectively. In study 2, 6 patients had biochemical failure, and all 6 developed metastatic disease. Actuarial 5-year biochemical failure was 0% for study 1 and 18.2% for study 2 (P = .005). There was no significant difference in the worst acute or late gastrointestinal or genitourinary toxicity. Grade 3 late genitourinary toxicity was noted in 3% of the patients in study 2 (HDR-BT boost). There was either no significant difference or minimal clinically important change in QoL. CONCLUSIONS: In the context of 5-fraction pelvic radiation therapy and ADT, there did not appear to be a significant difference in toxicity or QoL between SABR and HDR-BT boost. Although efficacy favored the SABR boost cohort, this should be viewed in the context of limitations and biases associated with comparing 2 sequential phase 2 studies.

Improved Ipsilateral Breast and Chest Wall Sparing With MR-Guided 3-fraction Accelerated Partial Breast Irradiation: A Dosimetric Study Comparing MR-Linac and CT-Linac Plans.

PURPOSE: External beam accelerated partial breast irradiation (APBI) is subject to treatment uncertainties that must be accounted for through planning target volume (PTV) margin. We hypothesize that magnetic resonance-guided radiation therapy with reduced PTV margins enabled by real-time cine magnetic resonance image (MRI) target monitoring results in better normal tissue sparing compared with computed tomography (CT)-guided radiation therapy with commonly used clinical PTV margins. In this study, we compare the plan quality of ViewRay MRIdian Linac forward planned intensity modulated radiation therapy and TrueBeam volumetric modulated arc therapy for a novel 3-fraction APBI schedule. METHODS AND MATERIALS: Targets and organs at risk (OARs) were segmented for 10 patients with breast cancer according to NSABP B39/RTOG 0413 protocol. A 3 mm margin was used to generate MR PTV3mm and CT PTV3mm plans, and a 10 mm margin was used for CT PTV10mm. An APBI schedule delivering 24.6 Gy to the clinical target volume and 23.4 Gy to the PTV in 3 fractions was used. OAR dose constraints were scaled down from existing 5-fraction APBI protocols. Target and OAR dose-volume metrics for the following data sets were analyzed using Wilcoxon matched-pairs signed-rank test: (1) MR PTV3mm versus CT PTV3mm plans and (2) MR PTV3mm versus CT PTV10mm. RESULTS: Average PTVs were 84.3 ± 51.9 cm3 and 82.6 ± 55 cm3 (P = .5) for MR PTV3mm and CT PTV3mm plans, respectively. PTV V23.4Gy, dose homogeneity index, conformity index (CI), and R50 were similar. There was no meaningful difference in OAR metrics, despite MR PTV3mm being larger than the CT PTV3mm in 70% of the patients. Average PTVs for MR PTV3mm and CT PTV10mm plans were 84.3 ± 51.9 cm3 and 131.7 ± 74.4 cm3, respectively (P = .002). PTV V23.4Gy was 99% ± 0.9% versus 97.6% ± 1.4% (P = .03) for MR PTV3mm and CT PTV10mm, respectively. Dose homogeneity index, CI, and R50 were similar. MR PTV3mm plans had better ipsilateral breast (V12.3Gy, 34.8% ± 12.7% vs 44.4% ± 10.9%, P = .002) and chest wall sparing (V24Gy, 8.5 ± 5.5 cm3 vs 21.8 ± 14.9 cm3, P = .004). CONCLUSIONS: MR- and CT-based planning systems produced comparable plans when a 3 mm PTV margin was used for both plans. As expected, MR PTV3mm plans produced better ipsilateral breast and chest wall sparing compared with CT PTV10mm. The clinical relevance of these differences in dosimetric parameters is not known.

Feasibility of breast radiation therapy in a Fanconi Anemia patient diagnosed with breast cancer: A case report and review of literature.

Fanconi Anemia (FA) is a rare inherited autosomal recessive disease that results in impaired double stranded DNA repair. This leads to both increased susceptibility to various cancers, as well as hypersensitivity to radiotherapy and systemic therapy; thus, increasing the complexity of oncological treatment paradigm. Here, we present an FA patient who initially developed invasive breast cancer for which she received breast conserving treatment with no significant treatment related toxicity. This was followed by a diagnosis of high-grade ductal carcinoma-in-situ in the contralateral breast, which was managed successfully by surgery and meticulously planned adjuvant radiotherapy, with no treatment interruptions.

Reduction of cardiac dose using respiratory-gated MR-linac plans for gastro-esophageal junction cancer.

Treatment of locally advanced adenocarcinoma of the gastroesophageal junction (GEJ) with chemoradiation may be associated with high rates of symptomatic cardiac toxicity. Large margins are typically required to ensure coverage of GEJ tumors with free-breathing volumetric modulated arc therapy (VMAT) radiotherapy. The purpose of this study is to determine whether treatment with tighter margins enabled by maximum-inhalation breath hold (MIBH)-gated intensity modulated radiation therapy (IMRT) on an integrated MRI-linear accelerator system (MR-linac) can decrease radiation doses to the heart and cardiac substructures. Ten patients with locally advanced GEJ adenocarcinoma underwent both free breathing 4-dimensional computed tomography (4DCT) and MIBH MRI simulation scans. MR-linac IMRT plans were created with a 3 mm clinical target volume (CTV) to planning target volume (PTV) isotropic margin and 4DCT VMAT plans were created with a 11, 13, and 9 mm CTV to PTV anisotropic margins in the left-right, cranial-caudal, and anterior-posterior directions according to GEJ-specific PTV expansion recommendations by Voncken et al. Prescription dose to PTV was 50.4 Gy in 28 fractions. Dosimetry to the heart and cardiac substructures was compared with paired t test; p < 0.05 was considered significant. Mean PTV on the MR-linac IMRT plans was significantly smaller compared to the 4DCT VMAT plans (689 cm3vs 1275 cm3, p < 0.01). Mean dose to the heart and all cardiac substructures was significantly lower in the MR-linac IMRT plans compared to the 4DCT VMAT plans: heart 20.9 Gy vs 27.8 Gy, left atrium 29.6 Gy vs 39.4 Gy, right atrium 20.5 Gy vs 25.6 Gy, left ventricle 21.6 Gy vs 29.6 Gy, and right ventricle 18.7 Gy vs 25.2 Gy (all p values <0.05). MIBH-gated MR-linac IMRT treatment of locally advanced GEJ adenocarcinoma can significantly decrease doses to the heart and cardiac substructures and this may translate to reduced rates of cardiac toxicity.

Evaluating dose constraints for radiation induced liver damage following magnetic resonance image guided Stereotactic Body radiotherapy.

This study reports dose corresponding to visible radiation induced liver damage following Stereotactic Body Radiation Therapy (SBRT) for liver metastasis, and the optimal time for follow up scans using post radiation imaging. Diagnostic magnetic resonance scans of nine patients treated with liver SBRT using a 0.35 T MRI-guided radiotherapy system were analyzed. The dice coefficients between the region of visible liver damage and the delivered dose were calculated. A median dose of 35 Gy correlated most closely with the visible radiation induced liver damage. We compared scans over two to nine months and observed maximal dice coefficients at two to five months post radiation. We have presented a new method for developing treatment planning guidelines for liver SBRT.

Stereotactic pelvic radiotherapy with HDR boost for dose escalation in intermediate and high-risk prostate cancer (SPARE): Efficacy, toxicity and quality of life.

BACKGROUND: The ASCO/CCO guidelines recommend brachytherapy (BT) boost for eligible intermediate- (IR) or high-risk (HR) prostate cancer (PCa) patients. We present efficacy, toxicity and quality-of-life (QoL) outcomes in patients treated on a prospective protocol of MRI dose-painted high-dose-rate BT boost (HDR-BT) followed by 5-fraction pelvic radiotherapy (RT) and 6-18 months of androgen deprivation therapy (ADT). METHODS: In this phase I/II study, IR or HR PCa patients received HDR-BT 15 Gy × 1 to prostate and up to 22.5 Gy to MRI nodule, followed by 25 Gy in 5, weekly fractions to pelvis. Toxicity was assessed using CTCAEv3.0, and QoL was captured using EPIC questionnaire. Biochemical failure (BF; nadir + 2.0), and proportion of patients with PSA < 0.4 ng/ml at 4-years (4yPSARR) were evaluated. A minimally clinically important change (MCIC) was recorded if QoL score decreased >0.5 standard deviation of baseline scores. RESULTS: Thirty-one patients (NCCN 3.2% favorable IR, 48.4% unfavorable IR and 48.4% HR) completed treatment with a median follow-up of 61 months. Median D90 to MR nodule was 19.0 Gy and median prostate V100% was 96.5%. The actuarial 5-year BF rate was 18.2%, and the 4yPSARR was 71%. One patient died of PCa. Acute grade 2 and 3 toxicities: GU: 50%, 7%, and GI: 3%, none, respectively. Late grade 2 and 3 toxicities were: GU: 23%, 3%, and GI: 7%, none, respectively. Proportion of patients with MCIC was 7.7% for urinary domain and 32.0% for bowel domain. CONCLUSIONS: This novel treatment protocol incorporating MRI dose-painted HDR-BT boost and 5-fraction pelvic RT with ADT is well tolerated.

Elective nodal ultra hypofractionated radiation for prostate cancer: Safety and efficacy from four prospective clinical trials.

BACKGROUND AND PURPOSE: The role of elective nodal irradiation (ENI) in localized prostate cancer (PCa) is controversial. With increasing use of SBRT to the prostate, data is needed regarding the safety and efficacy of ENI using ultra-hypofractionated radiation (UHRT). MATERIALS AND METHODS: Between 2013-2020, 4 prospective clinical trials of intermediate or high-risk PCa receiving dose-escalated RT to the prostate (via HDR brachytherapy or SBRT boost) and ENI using UHRT (25 Gy in 5 weekly fractions) were conducted. Primary endpoints included acute genitourinary and gastrointestinal toxicities (CTCAE v3.0/4.0), and secondary endpoints included late genitourinary and gastrointestinal toxicities, patient-reported quality of life (EPIC) and biochemical failure (Phoenix definition). RESULTS: One-hundred sixty-five patients were enrolled, of whom 98 (59%) had high-risk disease. ADT was used in 141 (85%). Median follow-up was 38 months (IQR 10-63). The worst acute genitourinary and gastrointestinal toxicities respectively were 48% and 7.5% for grade 2, and 2.7% and 0% for grade 3. Cumulative incidence of late grade 2+ genitourinary and gastrointestinal toxicities at 36 months were 58% and 11.3% and for late grade 3+ toxicities were 1% and 0%, respectively. No grade 4+ acute or late toxicities were observed. Bowel and sexual toxicity significantly worsened up to 1-year compared to baseline. Over time, urinary (p < 0.0001), bowel (p = 0.0018) and sexual (p < 0.0001) scores significantly improved. The 3-year biochemical recurrence-free survival was 98%. CONCLUSION: ENI using UHRT is associated with low incidence of grade 3+ toxicity, while grade 1-2 acute genitourinary and gastrointestinal toxicity is common. Randomized phase 3 trials are needed.

SABR in High-Risk Prostate Cancer: Outcomes From 2 Prospective Clinical Trials With and Without Elective Nodal Irradiation.

PURPOSE: There is limited data on stereotactic ablative radiation therapy (SABR) in high-risk prostate cancer (PCa), especially regarding the role of elective nodal irradiation (ENI). This study compares 2 prospective phase 2 trials using SABR in high-risk PCa, with and without ENI. METHODS AND MATERIALS: Patients had high-risk PCa. Those in trial 1 received 40 Gy in 5 fractions to the prostate and 30 Gy in 5 fractions to the seminal vesicles. Patients in trial 2 received 40 Gy in 5 fractions to the prostate and 25 Gy in 5 fractions to the pelvis and seminal vesicles. National Cancer Institute Common Terminology Criteria for Adverse Events toxicities were collected. Biochemical failure (BF) was defined as nadir + 2, and the 4-year prostate-specific antigen (PSA) response rate (4yPSARR) was <0.4 ng/mL. RESULTS: Sixty patients were included (trial 1, n = 30; trial 2, n = 30). Median follow-up was 5.6 years and 4.0 years. The median nadir PSA was 0.02 ng/mL for both trials. Six patients had BF, all from trial 1. The BF rate was 14.6% at 5 years in trial 1 and 0% in trial 2. Sixty-three percent of patients in trial 1 and 93% in trial 2 had a 4yPSARR. Two patients died in trial 1, 1 from metastatic disease. One patient in trial 2 died of other causes. No other patients developed metastatic disease, and 1 patient in trial 1 had castrate resistant PCa. Overall survival at 5 years was 93.2% and 96.7% (P = .86). There was significantly worse late gastrointestinal and sexual toxicity in trial 1, but there was no difference in late genitourinary toxicity. CONCLUSIONS: SABR in high-risk PCa yields biochemical control rates that may be comparable to that of other radiation therapy modalities. ENI using SABR is feasible and may lead to a significant improvement in biochemical control and in 4yPSARR, without an increase in late gastrointestinal or genitourinary toxicity. Longer follow-up would provide a better assessment of biochemical control. Well-conducted phase 3 trials are needed to fully establish the role of SABR and ENI in high-risk PCa.

Pre-treatment serum bicarbonate predicts for primary tumor control after stereotactic body radiation therapy in patients with localized non-small cell lung cancer.

BACKGROUND: Tumor aggressiveness and hypoxia are linked to acidosis in the tumor microenvironment (TME). We hypothesized that low pre-treatment serum bicarbonate, potentially correlating with an acidic and hypoxic TME, predicts for poor outcomes after stereotactic body radiation therapy (SBRT) for non-small cell lung cancer (NSCLC). METHODS: We included patients with localized NSCLC treated to a biologically effective dose (BED) ≥ 100 Gy, with available pre-treatment bicarbonate values within 3 months of treatment. We used receiver operating characteristic analysis to determine the bicarbonate concentration optimally predicting for primary tumor recurrence, and evaluated its association with recurrence and survival. We validated our findings in an independent cohort of patients from three collaborating institutions. RESULTS: A total of 110 patients and 114 tumors were included in the training cohort, with median follow-up of 15.0 months. Bicarbonate < 26 mEq/L was associated with primary tumor recurrence on univariate (HR = 5.92; 95% CI 1.69-24.88; p = 0.005) and multivariate analysis (HR = 5.48; 95% CI 1.37-25.19; p = 0.020). The validation cohort consisted of 195 patients and 208 tumors with median follow-up of 27.5 months. In the validation cohort, bicarbonate < 26 mEq/L was again associated with primary tumor recurrence on univariate (HR = 3.38; 95% CI 1.27-9.37; p = 0.015) and multivariate analysis (HR = 3.33; 1.18-10.07; p = 0.023). CONCLUSIONS: Pre-treatment bicarbonate predicts for primary tumor control in NSCLC treated with SBRT and may be useful for risk stratification. These findings should be confirmed prospectively.

A Feasibility Study on the Role of Ultrasound Imaging of Bladder Volume as a Method to Improve Concordance of Bladder Filling Status on Treatment with Simulation.

PURPOSE: Accurate positioning of the prostate is of paramount importance to ensure optimal target coverage and normal tissue sparing in stereotactic ablative body radiation when large doses per fraction are delivered with tight margins around the prostate. Bladder and rectal filling play an important part in controlling the accuracy of a patient's setup and therefore the overall toxicities and outcomes. The aim of this study was to establish the value of characterizing patients' bladder filling kinetics at the time of simulation with ultrasound scans so that a predictive model can be used to ensure that a bladder volume at treatment would match at simulation. METHODS: A prospective trial was conducted in unfavorable risk prostate cancer patients to evaluate the utility of ultrasound bladder monitoring. Thirty patients (n = 30) were enrolled in this study. Patients were required to void before simulation and then were given 500 mL of fluids to drink. Ultrasound measurements of the bladder were documented at 15-minute intervals for up to four measurements before simulation. On treatment, bladder volumes were measured at a single time point; typically, half an hour after the patient voided and consumed 500 mL of fluids. The kinetic model was then used to predict the optimal time to set up the patient for treatment such that the bladder volume at treatment would match the volume at simulation. Every patient had a cone beam computed tomography scan before each fraction to ensure accurate patient positioning before dose delivery. Bladder volumes at treatment were measured and compared with those at simulation on the cone beam computed tomography data sets using MIMVISTA software. RESULTS: Of 30 patients, 26 were analyzed. The comparison of the bladder contours at treatment compared to simulation yielded a DICE coefficient (similarity) of 0.76 ± 0.11. The largest variation in bladder size was seen in the anterior-posterior direction. CONCLUSIONS: This study demonstrated that ultrasound monitoring of the bladder status was a valuable tool in ensuring reproducible bladder filling on treatment. The bladder kinetic model indicated the general time required to achieve optimal bladder filling was 60 minutes after voiding and drinking 500 mL of water.

Phase 1-2 Study of Stereotactic Ablative Radiotherapy Including Regional Lymph Node Irradiation in Patients With High-Risk Prostate Cancer (SATURN): Early Toxicity and Quality of Life.

PURPOSE: Five-fraction stereotactic ablative radiation therapy appears to be gaining popularity in treatment of prostate cancer, but it has not been extensively tested in the context of pelvic radiation. The objective of this prospective prostate and pelvic SABR study is to report the acute toxicity, late toxicity, and quality of life (QoL) after study completion. METHODS AND MATERIALS: A phase 1/2 study was conducted for patients with high-risk prostate cancer. Radiation therapy was planned to deliver 25 Gy to pelvis and seminal vesicles (SV) and a simultaneous integrated boost (SIB) of up to 40 Gy to the prostate in 5 fractions, weekly, over 29 days. Androgen deprivation therapy was used for 12 to 18 months. Common Terminology Criteria for Adverse Events version 3.0 was used to assess worst acute and late toxicities. QoL data was captured using the Expanded Prostate Cancer Index Composite questionnaire (EPIC). RESULTS: Thirty patients completed the planned treatment with a median follow-up of 25.7 months (range, 18.5-30.7 months). The following "worst" acute and late toxicities were observed: grade 2 genitourinary toxicity, 46.7% and 52%, respectively; grade 2 gastrointestinal toxicity, 3.3% and 32%, respectively. No grade 3 or higher toxicities were noted. Mean (95% confidence interval) EPIC urinary QoL scores were 86.6 (81.9-91.3), 87.1 (81.4-92.6), and 87.9 (80.1-95.7) at baseline, 3 months and 24 months; bowel scores were 94.1 (91.3-97.0), 93.2 (89.1-97.2), and 92.4 (87.7- 97.1), respectively. CONCLUSIONS: This gantry-based novel fractionation schedule incorporating pelvic radiation for high-risk prostate cancer in combination with androgen deprivation therapy is feasible and well tolerated.